Printhead assembly having recessed printhead

ABSTRACT

A printhead assembly of a body and printhead is provided. The body has a first side, a second side opposed to the first side, the second side having a channel connected to a fluid supply, a recess separately defined in the second side, a plurality of passages defined through the body from the channel to the first side, and a plurality of fluid openings defined through the body from the first side to the recess, the fluid openings being individually connected to the channel via the passages. The printhead has fluid inlets connected to ejection nozzles, the printhead being received in the recess so that the fluid inlets interface with the fluid openings.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/435,372 filed May 4, 2009, now issued U.S. Pat. No. 7,878,627, whichis a continuation of U.S. application Ser. No. 11/075,918 filed Mar. 10,2005, now issued U.S. Pat. No. 7,543,924, which is a continuation ofU.S. application Ser. No. 09/922,105 filed on Aug. 6, 2001, now issuedU.S. Pat. No. 6,918,654, which is a continuation-in-part application ofU.S. application Ser. No. 09/113,053 filed on Jul. 10, 1998, now issuedU.S. Pat. No. 6,362,868 the entire contents of which are herebyincorporated by reference.

REFERENCES TO US APPLICATIONS

U.S. Pat. Nos. 6,362,868, 6,350,023 and U.S. patent application Ser. No.09/113,101, now abandoned,

FIELD OF THE INVENTION

This invention relates to ink jet printheads. More particularly, thisinvention relates to an ink jet printhead that incorporates through-chipink ejection nozzle arrangements.

BACKGROUND TO THE INVENTION

The Applicant has invented an ink jet printhead that is capable ofgenerating text and images at a resolution of up to 1600 dpi.

In order to achieve this, the Applicant has made extensive use of microelectro-mechanical systems technology. In particular, the Applicant hasdeveloped integrated circuit fabrication techniques suitable for themanufacture of such printheads. The Applicant has filed a large numberof patent applications in this field, many of which have now beenallowed.

The printheads developed by the Applicant can include up to 84000 nozzlearrangements. Each nozzle arrangement has at least one moving componentthat serves to eject ink from a nozzle chamber. The components usuallyeither act directly on the ink or act on a closure which serves topermit or inhibit the ejection of ink from the nozzle chamber.

The moving components within the printheads are microscopicallydimensioned. This is necessary, given the large number of nozzlearrangements per printhead. The Applicant has spent a substantial amountof time and effort developing configurations for such printheads.

One of the reasons for this is that, as is known in the field ofintegrated circuit fabrication, cost of on-chip real estate is extremelyhigh. Furthermore, it is important that levels of complexity are kept toa minimum since these significantly increase the cost of fabrication.

As a result of the need to keep on-chip real estate to a minimum, theApplicant has developed printhead chips that are extremely thin, havinga high length to width ratio. These chips are positioned end-to-end tospan a medium on which ink is to be deposited.

A substantial difficulty to be overcome with such printheads is thesupply of ink to the nozzle arrangements. A possibility investigated bythe Applicant was the provision of ink passages extending the length ofthe printhead chips, each passage carrying a different color. However,it will be appreciated by those of ordinary skill in the field of fluidmechanics that ink driven through such passages would be subject to anextremely high pressure drop. This pressure drop inhibits the ink frombeing carried at a suitably high flow rate. In FIG. 1 of the drawings,there is shown a printhead chip 1 incorporating three passages 2, onefor each color, extending the length of the printhead chip. The problemassociated with pressure drop in the passages is immediately apparent toa person of ordinary skill in the field of fluid mechanics, given thesmall cross sectional area of these passages.

An important requirement for the nozzle arrangements of this form ofprinthead is that they be refilled quickly once ink has been ejectedfrom the nozzle chambers. This ensures that the nozzle arrangements canre-fire in a very short time, leading to rapid printing, which is anadvantage sought by the Applicant. The high pressure drop mentioned inthe previous paragraph inhibits the development of a suitable flow rateto the nozzle chambers and consequent rapid re-firing.

In order to address this issue, one example of a printhead chip has rowsof ink inlet openings defined therein into which ink is fed. Each row ofink inlet openings corresponds to a differently colored ink. Thus, thenecessity of having ink flowing lengthwise in each chip is obviated.

For color printing, at least three different inks must be provided tothe printhead chip. These are Cyan, Magenta and Yellow inks. It iscritical that these inks are kept separate from each other up to thepoint of impact on the print medium since the printhead chip prints adithered image. It follows that it is necessary to provide each inletopening with an ink of a different color. This is shown schematically inFIG. 2. As can be seen in FIG. 2, this can be achieved by providing aprimary channel or reservoir 3 for each color. The ink from eachreservoir 3 is fed into smaller channels 4, which in turn feed into therows of ink inlet openings in a printhead chip 5.

It is to be appreciated that an ink distribution assembly comprising thereservoirs 3 and the smaller channels 4 must be manufactured with a highdegree of accuracy due to the small size of the channels in theprinthead chip 5 and the necessity for consistent ink flow to theopenings in the printhead chip 5.

One way of achieving this accuracy would be to machine the assembly outof silicon. However, Applicant has found that this would result in aproduct that is far too costly to be commercially competitive.

It follows that the assembly should preferably be molded of a plasticsmaterial. The principle forms of molding plastics material are extrusionmolding and injection molding. Applicant has found that extrusionmolding is not capable of producing a product that has the requiredaccuracy and structural stability for the assembly in question.

Substantial advances have been made in injection molding over the pastyears. Applicant has found that this form of molding can provide anassembly with the required accuracy and stability of construction.However, Applicant has identified a difficulty in injection molding anassembly having more than two reservoirs for ink. This is associatedwith the fact that it would appear that such a structure would requirethe construction of side mover cores when fabricating the molds to beused in the injection molding process. These cores are generally complexand expensive to manufacture. In FIG. 3, there is shown what would be anintuitive assembly including three ink reservoirs 6 molded in a plasticsmaterial, one for each ink of a particular color. It is clear thatinjection molding such an assembly would require the use of side movercores.

The Applicant has thus developed a distribution assembly that obviatesthe need for such side mover cores in its fabrication.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an inkdistribution assembly for a page width ink jet printhead in the form ofat least one printhead chip having sets of ink inlet openings, each sethaving at least one inlet opening for receiving an ink of a particularcolor to be supplied to the printhead chip, the assembly comprising

a carrier having an elongate structure with a printhead side that isengageable with the printhead and an opposed ink supply side, anddefining feed openings through the carrier to be in fluid communicationwith respective ink inlet openings of the printhead, the ink supply sideof the carrier defining a number of discrete feed formations, each feedformation being configured to receive ink of a particular color and tobe in fluid communication with the, or each, inlet opening of arespective set, via the feed openings, and the printhead side of thecarrier defining at least one ink supply formation, the carrier definingat least one passage in fluid communication between the, or each, inksupply formation and at least one of the feed formations; and

a cover that is engageable with the carrier at the ink supply side, thecover and the ink supply side of the carrier being shaped so that, whenthe cover is in position, the cover serves to define a roof for the feedformations and so that the cover and the ink supply side of the carrierdefine ink pathways that are in fluid communication with respective feedformations, one of the carrier and the cover defining ink supplyopenings in fluid communication with respective ink pathways.

According to a second aspect of the invention, there is provided amolded component for an ink distribution assembly for a page width inkjet printhead in the form of at least one printhead chip having sets ofink inlet openings, each set having at least one inlet opening forreceiving an ink of a particular color to be supplied to the printheadchip, the molded component comprising:

a carrier having an elongate structure with a printhead side that isengageable with the printhead and an opposed ink supply side, anddefining feed openings through the carrier to be in fluid communicationwith respective ink inlet openings of the printhead, the ink supply sideof the carrier defining a number of discrete feed formations, each feedformation being configured to receive ink of a particular color and tobe in fluid communication with the, or each, inlet opening of arespective set, via the feed openings, and the printhead side of thecarrier defining at least one ink supply formation, the carrier definingat least one passage in fluid communication between the, or each, inksupply formation and at least one of the feed formations.

According to a third aspect of the invention, there is provided a pagewidth printing device which comprises:

a page width ink jet printhead in the form of at least one printheadchip having sets of ink inlet openings, each set having at least oneinlet opening for receiving an ink of a particular color to be suppliedto the printhead chip;

a carrier having an elongate structure with a printhead side that isengageable with the printhead and an opposed ink supply side, anddefining feed openings through the carrier to be in fluid communicationwith respective ink inlet openings of the printhead, the ink supply sideof the carrier defining a number of discrete feed formations, each feedformation being configured to receive ink of a particular color and tobe in fluid communication with the, or each, inlet opening of arespective set, via the feed openings, and the printhead side of thecarrier defining at least one ink supply formation, the carrier definingat least one passage in fluid communication between the, or each, inksupply formation and at least one of the feed formations; and

a cover that is engageable with the carrier at the ink supply side, thecover and the ink supply side of the carrier being shaped so that, whenthe cover is in position, the cover serves to define a roof for the feedformations and so that the cover and the ink supply side of the carrierdefine ink pathways that are in fluid communication with respective feedformations, one of the carrier and the cover defining ink supplyopenings in fluid communication with respective ink pathways.

The invention is now described, by way of example only, with referenceto the accompanying drawings. The specific nature of the followingdescription is not to be construed as limiting the scope of this summaryin any way

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 shows a three dimensional view of a printhead chip incorporatingink supply passages extending a length of the chip;

FIG. 2 shows a layout of an ink distribution assembly that addresses theproblem of pressure drop within an ink jet printhead;

FIG. 3 shows a schematic end view of an ink distribution assemblyindicating problems associated with moulding such an assembly;

FIG. 4 shows a schematic view of an ink distribution assembly, inaccordance with the invention;

FIG. 5 shows a three dimensional, exploded view of a printing deviceincorporating an ink distribution assembly of the invention;

FIG. 6 shows a three dimensional view of a carrier for the inkdistribution assembly, from a printhead side of the carrier;

FIG. 7 shows a detailed view of the printhead side of the carrier;

FIG. 8 shows a three dimensional view of the carrier, from an ink supplyside of the carrier;

FIG. 9 shows a detailed plan view of part of the ink supply side of thecarrier; and

FIG. 10 shows a schematic, cross-sectioned view of the ink distributionassembly.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, FIGS. 1, 2 and 3 have already been discussed in thebackground to the invention above. These drawings indicate the provisionof three separate ink reservoirs in an ink distribution assembly and, inparticular, indicate the problems associated with molding such anassembly.

In FIGS. 4 and 5, reference numeral 10 generally indicates an inkdistribution assembly, in accordance with the invention, for an ink jetprinthead, indicated at 12. The printhead 12 can include one or moreprinthead chips 14 so that the printhead 12 defines a page widthprinthead.

The printhead chip 14 is the product of an integrated circuitfabrication technique. Furthermore, the printhead chip 14 incorporates alarge number of nozzle arrangements, each connected to drive circuitrywithin the printhead chip 14. The nozzle arrangements are each in theform of a micro electro-mechanical device that is operable upon receiptof a signal from the drive circuitry to eject ink from the nozzlearrangement. Details of the printhead chip 14 are clearly set out in theabove referenced applications. It follows that these details are not bedescribed in this specification.

The printhead chip 14 includes three sets or rows 16 of ink inletopenings 18 which are etched into a rear side 20 of the printhead chip14.

Each row 16 corresponds to ink of a particular color to be fed to theprinthead 12. In this particular example, the printhead 12 is configuredto accept cyan, magenta and yellow inks that are conventionally used forcolour printing. It will readily be appreciated that this invention isapplicable to those printhead chips that are configured to accept six oreven more differently colored inks.

The concept behind the present invention is indicated in FIG. 4.Broadly, the Applicant has provided a supply 11 for cyan ink and asupply 13 for yellow ink above a back side of the printhead 12 and asupply 15A and 15B of magenta ink on each side of the printhead 12. Thisarrangement permit the distribution assembly 10 to be manufactured in asingle shot injection molding process, as will become clear below.

The assembly 10 includes a carrier 22. The carrier 22 has a generallyplanar central portion 24 and a pair of opposed sidewall portions 26.The carrier 22 is elongate with the portions 24, 26 extending the lengthof the carrier 22.

The central portion 24 has an ink supply side 28 and a printhead side30. The printhead side 30 defines a retaining formation in the form of arecess 32. The recess 32 is dimensioned so that the printhead 12 is asnug fit within the recess 32.

The rows 16 of ink inlet openings 18 in the printhead chip 14 arereferred to in this specification as a central magenta row 34, an outercyan row 36 and an outer yellow row 38 of inlet openings 18. Thereference to the particular colors is simply for purposes of convenienceand ease of description. It will readily be appreciated that they can beinterchanged depending on the configuration of the printhead chip 14.

A floor 40 of the recess 32 defined by the carrier 22 has three rows 42,44, 46 of ink feed openings 48 defined therein. For the purposes of thisdescription, the row 42 will be referred to as the magenta row, the row44 will be referred to as the cyan row and the row 46 will be referredto as the yellow row. Again, it will be appreciated that this is simplyfor the purposes of illustration and ease of description.

The ink feed openings 48 are positioned so that, when the printhead 12is received in the recess 32, each ink feed opening 48 in the magentarow 42 is in register with a corresponding opening 18 in the magenta row34 of the printhead 12. The same applies to the cyan row 44 and theyellow row 46 of ink feed openings 48 with respect to the cyan row 36and yellow row 38 of ink inlet openings 18.

The ink supply side 28 of the central portion 24 of the carrier 22defines a magenta feed channel 50 with the magenta row 42 of ink feedopenings 48 defined in the magenta feed channel 50. In particular, apair of opposed longitudinal walls 54 that extend from the floor 52defines the magenta feed channel 50. Detail of the magenta feed channel50 and the walls 54 is shown in FIG. 9.

The printhead side 30 of the central portion 24 defines a pair of inksupply channels 56. The recess 32 is positioned between the ink supplychannels 56.

A plurality of laterally extending dividing walls 58 is connected to andextends from each wall 54. The dividing walls 58 are spaced to define aplurality of laterally extending, spaced ink feed channels 60 positionedon each side of the magenta feed channel 50. Each dividing wall 58 has anarrowed portion 62 proximate its respective longitudinal wall 54. Thus,each ink supply channel 60 widens at the longitudinal walls 54.

As can be seen in the drawings, there are two rows 66, 68 of the feedchannels 60. Again, for the purposes of illustration and ease ofdescription, the row 66 is referred to as the cyan row while the row 68is referred to as the yellow row. Thus, in keeping with thisterminology, there is provided a discrete cyan feed formation 70 on oneside of the magenta feed channel 50 and a discrete yellow feed formation72 on the other side of the magenta feed channel 50. Each ink feedopening 48 of the cyan row 44 and the yellow row 46 is defined inrespective feed channels 60.

The ink distribution assembly 10 includes a cover 78. The cover 78 has agenerally T-shaped cross section with a rectangular leg portion 80 and atop portion 82. The leg portion 80 is dimensioned to be received betweenthe opposed side wall portions 26 of the carrier 22. The leg portion 80has a flat bottom surface 84 which bears against the dividing walls 58to define a roof for the ink feed channels 60 and the magenta feedchannel 50.

As can be seen in FIG. 10, when the leg portion 80 is received betweenthe sidewall portions 26, an elongate, longitudinally extending inkpathway 86 is defined between each sidewall portion 26 and the legportion 80 of the cover 78.

Still further, each dividing wall 58 has a free end that is spaced fromits respective sidewall portion 26. It follows that each pathway 86 isin fluid communication with a row 66, 68 of ink feed channels 60. Again,for the purposes of illustration and ease of description, the pathways86 are referred to as a cyan pathway 88 and a yellow pathway 90. One end92 of the carrier 22 has three inlet openings defined therein. Theseare, again for the purposes of convenience, referred to as a centralmagenta inlet opening 94, a cyan inlet opening 96 and a yellow inletopening 98.

When the cover 78 is in position, the cyan inlet opening 96 is in fluidcommunication with the cyan pathway 88. Likewise, in this condition, theyellow inlet opening 98 is in fluid communication with the yellowpathway 90. It will therefore be appreciated that an ink flow path isdefined from the openings 96, 98, to the rows 36, 38 of ink inletopenings 18 in the printhead 14 via the pathways 88, 90, the feedchannels 60 of the rows 66, 68 and the openings 48 of the rows 44, 46.

Each of the dividing walls 58 has a magenta ink flow passage 100 definedtherein, which is in fluid communication with one of the ink supplychannels 56. Further, each dividing wall 58 has a magenta conduit 102defined therein, one end of which is in fluid communication with arespective magenta ink flow passage 100 and the other end of which is influid communication with the magenta feed channel 50. It follows thatthe dividing walls 58 and the longitudinal walls 54 define a magentafeed formation 116.

A pair of magenta ink supply openings 104 is defined in the centralportion 24 proximate said one end 92 of the carrier 22. The leg portion80 is configured so that when the cover 78 is in position, the magentainlet opening 94 is in fluid communication with both of the magenta inksupply openings 104.

It will therefore be appreciated that an ink flow path is definedbetween the magenta inlet opening 94 and each of the ink inlet openings18 in the magenta row 34 of the printhead 14 via the magenta ink supplyopenings 104, the ink supply channels 56, the magenta ink flow passages100, the magenta conduits 102, the magenta feed channel 50 and theopenings 48 in the magenta row 42.

It will further be appreciated that each of the feed formations 70, 72,116 defines a pathway that is repeatedly divided into narrower portionsas the ink approaches the printhead 12.

The assembly 10 includes a pair of cover plates 106 which are fastenableto the printhead side 30 of the central portion 24 to form roofs for theink supply channels 56. In FIG. 5, there is shown a printing device thatincorporates the assembly 10. The printing device, for example, includesa tape automated bonding (TAB) strip that connects the drive circuitrywithin the printhead 12 to a control system (not shown) to controloperation of the printhead 12. Further, an outer side 108 of eachsidewall portion 26 defines guide formations 110 for rollers 112. Therollers 112 are used to drive a print medium 114 past the printhead 12during printing. Details of the TAB strip and the rollers are set out inthe above referenced applications. It follows that these details are notdescribed in this specification.

The carrier 22 is the product of an injection molding process. Thecarrier 22 can thus be of a thermoplastics material or of athermosetting material.

In its broadest terms, injection moulding requires the injection of ahot liquid resin or a thermosetting resin into a closed mould, underpressure, until the moulded part is cooled or cured and can be ejectedfrom the mould.

As is known to those of skill in the field of moulding, it is desirableif a component to be moulded can be moulded by a machine requiring onlymovement to and fro in a single direction. In general, such machinescomprise a rear platen, a moving platen and a stationery platen. Diesare positioned between the moving platen and the stationery platen anddefine, between them, a volume into which pre-molded material isinjected.

In the event that a component is required to have an enclosed volume andbe injection molded, it is often necessary to provide what are known asside mover cores that operate together with the moulding machinery togenerate the component having the included volume. Such side mover coresare known to be extremely expensive and complex both to manufacture andto operate.

In the present invention, it would be intuitive to provide threedistinct enclosed volumes, as shown in FIG. 3, for the provision of inkreservoirs from which ink is supplied to each of the rows 34, 36, 38.However, it is clear that an injection-molding machine to generate thisform of molding would require side mover cores. This could result in thecomponent being excessively expensive and complicated to manufacture,especially on a mass basis.

The present invention is based on an idea conceived by the Applicant ofdefining such an enclosed volume or reservoir on the printhead side 30of the carrier 22. The difficulty with this is to provide an ink flowfrom the printhead side 30 of the carrier 22 to the ink supply side 28.Applicant has achieved this with the present invention.

It is apparent both from the above description and the drawings that itwould be clear to a person of ordinary skill in the field of injectionmolding that the carrier 22 can be manufactured using a standardinjection-molding machine without the requirement for side mover cores.

As is also clear from the drawings, the cover 78 is of a relativelysimply shape and can also be manufactured with a standardinjection-molding machine.

Applicant believes that the invention provides a means whereby an inkdistribution assembly for a page width ink jet printhead can be achievedwhich lends itself to a simple, one-shot injection molding process. Thishas far reaching cost implications as printing devices incorporatingsuch ink distribution assemblies are intended for mass manufacture.

1. A printhead assembly of a body and printhead, the body having: afirst side; a second side opposed to the first side, the second sidehaving a channel connected to a fluid supply; a recess separatelydefined in the second side; a plurality of passages defined through thebody from the channel to the first side; and a plurality of fluidopenings defined through the body from the first side to the recess, thefluid openings being individually connected to the channel via thepassages, and the printhead having: fluid inlets connected to ejectionnozzles, the printhead being received in the recess so that the fluidinlets interface with the fluid openings.
 2. A printhead assemblyaccording to claim 1, wherein the body is elongate, the channels and thefluid openings being arranged along the length of the body.
 3. Aprinthead assembly according to claim 2, wherein the fluid openings arearranged in a row.
 4. A printing device comprising the printheadassembly of claim 1.